Warrumbungles, New South Wales, Australia

Location: 30.5S, 150.5E

The shield volcano that made the Warrumbungles was active about 13-17
million years ago. It rose 3,000 feet (1,000 m) above the surrounding
country. Most of the volcano has been eroded, exposing the interior
plumbing of small plugs and dikes. This photo shows Belougery Spire, a
trachyte plug. A plug is the erosional remnant of a pipe
that fed a volcano. Photograph by C. Ollier.

The Breadknife is dike, a tabular-shaped fracture that cuts across
pre-existing rock and fed magma towards the surface. The Breadknife is near
2,000 feet (600 m) long and made of trachyte. Photograph by C. Ollier.

The volcanic features are part of Warrumbungle National Park. Photograph by
C. Ollier.